I. Field of the Invention
The present invention relates to a method for the detection and classification by type of heavy hydrocarbon contaminants in petroleum refinery process streams using spectrofluorometry.
II. Description of the Prior Art
There are numerous, industry-accepted test methods for the analysis of physical and chemical properties of hydrocarbons which, alone or in combination, have been used to detect the presence of hydrocarbon contaminants in various refinery process streams and/or to classify them as to type. These methods have been approved by organizations such as ASTM (American Society for Testing Materials), IP (Institute of Petroleum, United Kingdom), and DIN (Deutsches Institut fur Normung, Germany), as well as private companies which provide analytical instrumentation or which license processes to refineries. These would include methods such as: ASTM D-86 distillation temperatures at various percentages distilled; ASTM D-1298 test for API gravity; Gas chromatography—Mass spectrometry (GC Mass Spec) for determination of weight percent aromatics; and ASTM D-2622 for sulfur, ASTM D3710-95 Boiling Range Distribution of Gasoline and Gasoline Fractions; ASTM D2789-25 Hydrocarbon Types in Low Olefinic Gasoline by Mass Spectrometry; ASTM D4534 Benzene Content of Cyclic Products; ASTM D5134-92 Detailed Analysis of Petroleum Naphtha through n-Nonane by Capillary GC; ASTM D5443-93 Paraffin, Naphthene and Aromatic Hydrocarbon Type Analysis in Petroleum Distillates; ASTM D5769-95 Determination of Benzene, Toluene and Total Aromatics in Finished Gasoline by GC/MS; ASTM D6293-99 Oxygenates and Paraffin, Olefin, Naphthene, Aromatic (O-PONA) Hydrocarbon Types in Low-Olefin Spark-Ignition Engine Fuels by Gas Chromatography; ASTM D6296-98 Total Olefins in Spark-Ignition Engine Fuels by Multi-dimensional Gas Chromatography; IP 382/88 Paraffin, Naphthene and Aromatic Hydrocarbon Type Analysis in Petroleum Distillates; IP BG/91 (proposed) Determination of methyl tertiarybutyl ether and tertiaryamyl methyl ether in Light Distillate Feedstock; DIN, 51.448, part 2 Paraffin, Naphthene and Aromatic Hydrocarbon Type Analysis in Petroleum Distillates; DIN Method, 51.448 part 2, Oxygenates and Paraffin, Olefin, Naphthene, Aromatic (O-PONA) Hydrocarbon Types; UOP 870 Paraffin, Naphthene and Aromatic Hydrocarbon Type Analysis in Petroleum Distillates; High Speed Simulated Distillation of Light Hydrocarbons, Gasoline and Gasoline Feedstocks; Detailed Hydrocarbon Analysis (DHA) of Non-Oxygenated Gasoline and Hydrocarbon Liquids using stream dedicated databases; High Speed Detailed Hydrocarbon Analysis of Non-Oxygenated Gasoline and Hydrocarbon Liquid; Individual Hydrocarbon Analysis of Gasolines and Light Fractions (PIANO/IHA/DHA) by Gas Chromatography; High Speed Detailed Hydrocarbon Analysis of Non-Oxygenated Gasoline and Hydrocarbon Liquids; DHA of Oxygenated Gasoline and Gasoline Feedstocks; Simultaneous Nitrogen and Hydrocarbon Analysis by GC with Flame Ionization and Chemiluminescence Detection in Light Petroleum Liquids; Sulfur Compounds in Distillates by GC-Chemiluminescence Detection; Sulfur Distribution in Petroleum Distillates by Simultaneous HPLC-UV and Chemiluminescence Detection; Nitrogen, Sulfur and Carbon Distribution in Distillates by GC-Chemiluminescence and Flame Ionization detection; Multi-Elemental Boiling Point Distribution Analysis Using the Atomic Emission Detector (AED) on Petrochemical Samples with a Final Boiling Point Below 650° F.; Sulfur and Carbon Distribution in Light Petroleum Products by Simultaneous GC-FID and GC-Sulfur Specific Detection; Low level S analysis -ppm to sub-ppb; Analysis of Paraffins in Kerosene (C5-C20) by Subtractive Gas Chromatography; PIANO analysis of gasoline and gasoline boiling-range blending streams, automatic peak ID and reporting; High Speed Contaminant Analysis Using Mass Spectrometry with Matrix Deconvolution; Aromatic and Saturate Types in Petroleum Distillates.
Conventionally, these tests are conducted using many different types of apparatuses. These tests are time-consuming and relatively expensive. These tests also lack sensitivity to detect contaminants at low concentrations and lack specificity to determine the type of contaminant. The contamination of light refinery process streams with heavy aromatics is an ongoing concern in the petroleum industry. Such contamination can cause severe processing problems and/or result in final products which do not meet contractual or government specifications. To mitigate and control this problem in particular, it is desired to detect the presence and type of the heavy aromatics and to identify its source. Often, the source of contamination is one or more heat exchanger leaks occurring in the system.
Detection and classification is complicated by the fact that there are both gas oil exchangers and crude oil exchangers and the materials in these exchangers both fluoresce in the same wavelength range. It is to be noted that exchanger leaks on the crude units typically occur on two-year cycles due to the age of the exchangers (basically, once the exchangers begin leaking, the exchangers are replaced). It is, therefore, important to find the correct exchanger, which can be difficult (especially if more that one is leaking). Past exchanger leak episodes and their detection have been marginally successful. Often detection of the exchanger leak was more due to operator knowledge than successful use of other methods. The instruments being used could only detect that there were heavy aromatics in the stream; however, there was no identification of the types of heavy aromatics that were present.
It is desired, therefore, to have an on-line testing apparatus installed on or “at” a feedstock stream to monitor the degree of contamination and the type of contaminant.